Psychological horror film The Shining is one of the beacons of its genre, cited as one of the best films of all time, and selected for preservation by the U.S.’ National Film Registry for its “cultural, historical or aesthetical” significance.

As famous as the film itself is, perhaps, one of his scenes. It’s a terrifying, intense and disturbing sequence - which many don't realise was improvised by the cast.

Disappointed with the box office flop of his previous film Barry Lyndon (1975), Stanley Kubrick wanted to work on a film that would not let him down artistically, but that would be commercially viable and appealing to audiences.

According to Stephen King, he then locked himself with a pile of horror novels to go though, in search of the perfect story: “Kubrick's secretary heard the sound of each book hitting the wall as the director flung it into a reject pile after reading the first few pages. Finally, one day the secretary noticed it had been a while since she had heard the thud of another writer's work biting the dust. She walked in to check on her boss and found Kubrick deeply engrossed in reading a copy of the manuscript of [King’s] The Shining".

From then on, production was on course. Kubrick enlisted Shelley Duvall, Danny Lloyd, Scatman Crothers and Barry Nelson to join his main star Jack Nicholson in the movie - which told the story of Jack Torrance, a recovering alcoholic and aspiring writer who takes a job as the winter caretaker of the isolated Overlook Hotel with his wife Wendy and their psychically gifted son Danny.

The hotel's sinister history and evil presence begin to corrupt Jack, while Danny experiences terrifying visions and glimpses of the hotel's true nature through his psychic abilities. As Jack descends into madness, Wendy and Danny are trapped and endangered by the hotel's malevolent forces.

The film’s most famous scene happens as part of its climax, when Jack places his face through a broken door to get to a member of his family and says, "Here's Johnny!"

As Kubrick is known for going through as many takes as possible to get to a perfect scene, this particular moment reportedly took three entire days to shoot - and about 60 doors.

That was when, during one of those repetitions of the same lines, Nicholson ad-libbed “here’s Johnny” - even though no characters in the movie were named Johnny, and he is said to have taken inspiration from popular late-night television program The Tonight Show Starring Johnny Carson.

Kubrick, who had been in the UK while the show was on air, did not understand the reference and chose to keep the improvised line in the final cut.

Since then, the scene became arguably bigger than the film it comes from - with references in modern art and more recent pop culture products -, and served as an opening to the Johnny Carson Show’s 18th anniversary.